Digitally printed original documents may incorporate numerous forms of security features to verify the authenticity of the original documents as originals. Such security features may include microprint, void pantographs, watermarks, guilloche, verification grids, covert security such as HALO image (available from ARCIS Solutions Inc.), feature registration on opposing sides of paper and latent images view-able using special filters. These features can be embedded into a document, wherein the feature may not be visible to the casual observer and often requires some degree of manipulation to be seen. For example, photocopying or scanning may reveal void pantographs and may alter or eliminate microprint, verification grids, watermarks, and guilloche images; special lenses or filters may reveal covert images or alter Halo images.
Of the techniques noted above, void pantographs are commonly used. In the past, this feature can only be produced using standard press printing processes such as, but not limited to, offset web and sheet fed printing (lithography), letterpress, flexographic, intaglio and gravure. The press printing processes may include generating film or plate, as in the case of CTP (computer to plate), at very high resolution usually at 2400 or 2540 dpi (dots per inch) and beyond; to produce patterns of dots, lines, screen structures or the likes that is required in a void pantograph. Recently, advancements have been made in void pantograph creation (such as described in but not limited to U.S. Pat. Nos. 7,307,761; 7,869,090; 8,164,799; 8,405,882; 8,593,698; 8,743,425; 8,817,330; 8,891,136; 9,738,106; etc.), so that this feature can be printed using laser printers (including laser copier/printer), ink-jet printers, direct image presses, production digital presses and combinations thereof, such as the Canon ColorStream, i300, VP 6000, VP10000, Ricoh InfoPrint 5000, 40000, 60000, HP Indigo, Screen Truepress series, Xeikon, and the Xerox IGen, Rialto 900, Brenva, Fiji J Press, at lower resolutions, as low as 300 dots per inch, and up.
Void pantographs utilize halftone elements, such as dots or lines, varying in size or spacing to form halftones that provide the visual appearance of a continuous tone or color gradients. The halftone elements provide a covert copy evident feature, which appears when the document is reproduced. The alteration of the size and placement of the elements in the halftones may trick the optic engine of copy machines and scanners. In embodiments, at least one set of the halftone elements is difficult to reproduce using these methods. Accordingly, when reproduced, a portion of the elements (such as the larger elements or elements placed more closely together are reproduced in a manner that makes them stand out from the continuous tone of the void pantograph due to, for example, a failure to reproduce the remainder of the elements, which dropout. This may reveal words such as “COPY”, “VOID”, “INVALID” or images such as logos upon copying.
However, as noted above, void pantographs are generally applied to a document as a background and appear to be a continuous tone of one color or it's tonal gradients, where text and other graphics appear on top of such a background to form a finished document such as a check, permits, coupon, transcript, etc. Sometimes, the void pantograph is provided in what would appear to the casual observer as a flat tint or one uniform color and may sometimes include a camouflage pattern on top of a flat tint to create a regular or irregular texture.
Void pantographs for the digital printing platform are not understood to provide images that exhibit numerous colors, saturation levels, and brightness values visible to the casual observer as it is difficult to provide both the image and the copy-evident features of the void pantograph. In addition, even when void pantographs are provided in patterns, textures, and images, they generally require careful configuration to keep the void pantograph covert and maintain its effectiveness upon reproduction. Therefore, only a few patterns and textures are generally available and it is difficult to fully customize the images visible to the casual observer upon replication. Thus, there remains room for improving the provision of void pantographs in documents to improve their customizability and variability.